Project Summary We request partial support for the 21st Chronobiology Gordon Research Conference (GRC) and the accompanying 4th Gordon Research Seminar (GRS), which will be held at the Rey Don Jaime Grand Hotel, Castelldefels, near Barcelona, Spain from June 23-28th 2019. Any funds that we receive from the NIH will be used to partially support the registration fees for predominantly younger researchers, postdoctoral fellows and graduate students who will attend the GRC and associated GRS. The Nobel Prize in Medicine or Physiology awarded in 2017 to our colleagues Jeff Hall, Michael Rosbash and Mike Young for their pioneering work in deciphering the molecular basis of the circadian clock ensures that both GRC/GRS will attract a wide-range of researchers working at many different levels with diverse methodologies and model organisms. The GRS will focus on training and mentorship, while the GRC will present the latest unpublished work from the senior and emerging stars of the field. The GRC subtheme is `Clocks in model organisms: Circadian Networks, Physiology and Health' and emphasizes the diverse range of organisms that are studied from many different perspectives, from the molecular, cellular, physiological to behavioral and population layers. This also includes the application of these findings to the clinic and workplace. Consequently there is a wide range of topics covering most aspect of chronobiology using a diverse range of organisms and research methodologies included within the program. In higher organisms, the master circadian clock is in the brain, and chronic circadian disruption by modern lifestyles has important implications for human behavior, metabolism and healthy ageing, so the conference fits well within the sphere of NINDS, NIA and NIDDK. The speakers and discussion leaders represent senior established figures and younger emerging stars of the field and have been selected by consultation with an informal committee consisting of both senior and more junior figures in the field. There is an almost equal number of male and female speakers/session chairs as well as a range of nationalities invited to speak, from the Americas, Europe and the Far East ensuring a cultural and gender diversity. Apart from the mentorship, the GRS will also have 8 junior speakers and the GRC will further select 9 abstracts from younger scientists for presentation as short talks at the main meeting, providing an important learning experience for the trainees.